Single phase power supply systems throughout Australia and in many parts of the world comprise an active conductor and a neutral conductor which is generally maintained at earth potential by being connected to an earthing system at various points throughout the distribution system, including at a consumer's switch board.
A potential fault situation which sometimes arises and which may be of a major concern to the supply authority and the power user is that of reverse polarity. Reverse polarity may occur through reversing the neutral and active connections at the electricity meter on the premises of the user or at the supply pole from which the service is supplied. With a reverse polarity fault condition, an extremely hazardous situation occurs as dangerous active voltage may be present on the neutral, giving rise to dangerous voltage levels present on the earth system of the user. Many earth systems are connected through water pipes and the like which, in the event of a reverse polarity fault, will give rise to extremely hazardous conditions.
Another fault situation which can create hazardous conditions for the electricity user is that of a neutral failure. If, for example, the neutral wire connecting the user's premises to the power system is accidentally disconnected, such as by a tree or the like cutting the wire, all of the current flow is forced into the user's earth system rather than the neutral connection. This can create the problem of a hazardous voltage on the user's earth, particularly if an earth connection has a higher than expected resistance.
A further potentially hazardous fault situation is a broken or high resistance customer earth system.
At the present time, such fault conditions can only be ascertained by conducting specific fault tests on consumer's premises. Such testing is time consuming and expensive and is, therefore, carried out very infrequently if at all. The faults referred to are not detected by the standard, mechanical electricity meter, or in house Residual Current Device (RCDs).
Accordingly, it is desirable to provide a system which can detect predetermined fault conditions which are present on or arise in a consumer's premises.
It is also desirable to provide a method and system for detecting fault conditions that does not require physical change to be made to a consumer's switchboard or meter board.
It is also desirable to provide a system, and method, to constantly monitor the power supply to a consumer's premises and detect predetermined fault conditions. It is also desirable to provide a method and system which may be adapted to disconnect a supply to a consumer's premises on detection of predetermined fault conditions.
It is also desirable to provide a system and method for detecting predetermined fault conditions associated with the power supply to a consumer's premises which is relatively simply, easy and economic to implement.